The present invention relates to an apparatus for recapping tires. More particularly, the invention relates to a variable machine for rasping, a machine for capping a tire, or a machine comprising a rasper combined with units for applying and rolling treads.
It is known that most tires can be recapped, i.e., after normal wear of the tread, it is possible to replace the tread, and even certain reinforcement plies of the tire. These operations are very common for the tires of transport vehicles, such as heavy goods vehicles, and can be carried out in factories, or in workshops of a greater or smaller size, where problems of dimensions become fundamental.
Many machines which are designed to remove the worn remainders of the tread of tires, an operation which is known as tread removal, have been proposed, as well as so-called capping machines, which are designed to apply a new tread to the tires from which the tread has previously been removed.
At present, there is an increasing demand for “flexible” machines, which can recap tires with different dimensions, and in particular tires which are increasingly wide, both in the case of tires of which the tread extends only on the crown, and that of tires of which the tread also covers the shoulders of the tire, a tread of this type being known as of the “flap” type. This dual constraint of size and geometry poses genuine problems, in terms of the dimensions of the machine, feasibility for flap-type treads, and quality of the recapping carried out.
In fact, the recapping machines which are commonly sold commercially have a frame with vertical lateral flanges, surrounding the tire which is generally disposed vertically. In order for a machine of this type to be able to recap large tires, it is necessary to increase considerably the size of the machine, and thus its dimensions.
Furthermore, the presence of these lateral uprights makes it difficult to access the shoulders of the tire. In order to carry out the tread removal, use is often made of a robot which supports a rasp, but in this case also an increase in the size of the tire gives rise to an increase in the length and rigidity of the arm of the robot which supports the rasp, and consequently gives rise to problems of stability and vibrations, which detract considerably from the quality and accuracy of the work carried out by a machine of this type.
Other types of machines have been proposed, such as that described by way of example in publication AU-1 528 470, in which the frame of the machine comprises a mandrel which rotates and is fixed in translation, which supports the tire in front of which there is displaced in axial and radial translation relative to the axis of the mandrel, a rotary rasp which is guided by means of a template. The disadvantage of using a template is known, associated with the need to change the template in order to accompany a change of dimension of the tire to be recapped, and thus with successive operations of removal and fitting. In addition, the problems of length of the arm which supports the rasp, and thus of stability and vibration, are not solved in this case, since accessibility to the shoulders of the tire is limited by the structure of the machine itself.
Publication EP-0 955 154 presents a different solution, in which the machine has a rotary mandrel which can be displaced in translation, according to a vertical axis which is perpendicular to the rotational shaft of the mandrel, and rotary rasping tools which are fitted above the tire, and can also be displaced in horizontal translation, parallel to the rotational shaft of the mandrel, the axis of the rasping tools being perpendicular to that of the mandrel (FIG. 4 of the publication), in order to permit rasping of the shoulders of the tire to be recapped, if necessary.
In fact, the combination of these two movements of translation makes it possible to carry out the tread removal of a tire which has a flap-type tread, which requires production of a complex profile, with a radius of curvature at the crown, other radii of curvature at the shoulders, and finally a trapezium in order to carry out the descent from the shoulders to the sidewalls. However, this machine does not provide solutions for the problems of vibrations and stability. In fact, for a tire of large size, which is also heavier, the vertical movement of the mandrel can give rise to problems of stability, or even risk giving rise to slight flexure of the rotational shaft of the mandrel. In addition, in order to permit satisfactory access to the shoulders which are disposed opposite the post on which the mandrel is fitted in translation, it is necessary to be able to move the tire sufficiently far away from the post, axially relative to the axis of the mandrel, which increases the risks of a phenomenon of this type occurring.
In order for the machine to function for a very wide tire, it is also necessary to have extended the guide rails for the rasping tools, which are suspended above the tire, thus giving rise to greater vibrations during translation and actuation of these rasping tools.